Expansion of tubes into tube sheet by use of explosives



R. M. OLIVER Feb. 11, 1969 EXPANSION OF TUBES INTO TUBE SHEET BY USE OF EXPLOSIVES Filed June 15, 1967 INVENTOR. RICHARD M OL/l EE Wi M ATTOQNE) United States 3,426,681 EXPANSION F TUBES INTO TUBE SHEET BY USE OF EXPLOSIVES Richard M. Oliver, Chattanooga, Tenn., assignor to Combustion Engineering, Inc., Windsor, Conn., a corporation of Delaware Filed June 15, 1967, Ser. No. 646,220 US. Cl. 102-24 Int. Cl. F42b 3/00, 1/02 3 Claims ABSTRACT OF THE DISCLOSURE A polyethylene tube which houses explosive means to be used for explosively expanding metallic tubes into a metallic tube sheet. The polyethylene tube is closed at its end which extends into the metallic tube, and has an air pocket therein to prevent the end from being ruptured, which would expose the interior of the metallic tube to the explosive residue.

Background of the invention Summary of the invention In accordance with my invention a resilient polyethylene tube is provided for acting as a pressure cartridge in explosively expanding metallic tubes into a metallic tube sheet. The resilient tube is closed at its end which extends into the metallic tube, and has an air pocket therein to prevent the end from being ruptured, thereby preventing the contamination of the metallic tubes by the explosive residue. The pressure cartridge contains a collar thereon for engaging the metallic tube end, thereby properly positioning the cartridge and the explosive. A hole and slot in the cartridge permits the use of a simple tool for quickly and accurately connecting a detonation cord to the explosive.

Brief description of the drawings FIGURE 1 is a cross-sectional side view of a tube sheet to which a plurality of tubes are to be explosively secured using apparatus of the invention;

FIGURE 2 is an enlarged view in section of a single explosive charge, and the pressure cartridge in which it is housed;

FIGURE 3 is a sectional view taken on lines 3-3 of FIGURE 2;

FIGURE 4 is a front elevational view taken on lines 4-4 of FIGURE 1; and

FIGURE 5 is an enlarged view in section showing the manner in which the detonating cord is assembled with respect to the pressure cartridge and the explosive charge.

Description of the preferred embodiment Referring now to FIGURE 1, designates a tube sheet containing bores therein in which a plurality of tubes 12 are to be anchored or secured by explosive expansion. In order to accomplish the explosive expansion, pressure cartridges 14 are positioned within each of the tubes, containing explosive means 16. The cartridge is 3,426,681 Patented Feb. 11, 1969 in the form of a resilient, low density polyethylene tube, and the explosive is a Primacord fuse, preferably of PETN (pentaerythritol tetranitrate) Each cartridge has a collar 18, which is of such size that it will not enter the metallic tubes 12. Thus when an explosive charge of a given length is inserted in the cartridge, it being fiush with the left end of the cartridge (FIGURE 2), and the cartridge is inserted into a tube 12 until the collar 18 engages the tube end, the explosive charge is accurately positioned. The collar also performs the function of preventing the cartridge from being propelled into the tube 12 when the explosive is detonated. Cartridge 14 has a closed end.22, which prevents any residue from the explosion from entering the tube 12.

It has been found that when an air gap 20 has been left in the cartridge, the end 22 will not be blown out during the explosion. Without this air cushion, end 22 frequently was ruptured, resulting in contamination of the interior of tube 12. When the tube sheet thickness is approximately two feet, an air gap 6 to 12 inches in length is desirable.

Looking again to FIGURES 2 and 3, the manner in which the explosive charge is detonated will now be explained. Cartridge 14 has a hole 24 therein which is transverse to and intersects the bore containing the explosive charge. A slit 30 extends from the hole 24 to the outer periphery of the cartridge, throughout approximately a arc. By bending the left-hand end of the cartridge downwardly, a length of detonating cord 26 can be slipped down between the separated interfaces of slit 30 into the hole 24 (see FIGURE 5). A tool 32, which can be merely a piece of pipe slipped over the end of the cartridge, can be used for bending the end down. The hole 24 is of such a size with respect to detonating cord 26, and overlaps the longitudinal bore such that the two cords are clamped in very tight engagement with one another when the end of the resilient cartridge is disengaged. This insures the detonation of the explosive charge within the cartridge by the detonating cord.

It is possible to detonate a plurality of charges simultaneously by means of a single detonating cord. As seen in FIGURE 4, cord 26 is in engagement with a number of explosive charges, with one end running to a suitable detonating device 28. A preferable detonating means is a dynamite cap.

The manner in which a plurality of tubes 12 are expanded into passageways in a tube sheet 11 will now be explained. First, a plurality of tubes 12 are positioned in the passageways with the left-hand ends flush with the end of the tube sheet. Then cartridges 14 containing explosive means 16 are inserted into each tube 12, with collars 18 abutting the tube ends. A detonating cord is then secured to each cartridge by means of hand tool 32, and one end is connected to ignition or detonating means 28. Upon detonation of the explosives, the polyethylene cartridges expand, causing expansion of tubes 12 into tight physical engagement with the walls of the passageways of the tube sheet 10.

Some care should be taken in selecting the properly sized polyethylene tube, and the size of the explosive charge, in order to get a sufficiently sized explosion to tightly expand the tube within the tube sheet, while preventing the cartridge from rupturing and contaminating the interior of the tube.

As one example, inconel tubes having a wall thickness of .05 and outer diameter were expanded into a twenty-two inch thick carbon steel tube sheet, having bores or passageways which are a few thousands of an inch larger than the tube outer diameter. A polyethylene cartridge which snugly fits in the tube bore was used, and a nine inch air gap was left in the cartridge bore between the explosive charge and the closed end of the cartridge, which end or plug was approximately /2" thick. A 12 grain per foot PETN Primacord was positioned within a .15 bore in the cartridge. The results of the explosion was a tightly secured tube, which had been equally expanded over the entire surface positioned within the tube sheet. The explosive charge should not extend past the end 01": the tube sheet, or it will cause bulging of the tube at this point.

While I have illustrated and described a preferred embodiment of my invention, it will be understood that minor changes in construction and arrangement of parts may be made without departing from the spirit and scope of the invention as claimed. It is therefore intended that all matter contained in the description or shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense.

What I claim is:

1. Means for explosively expanding a first metallic tubular member into good physical contact with another concentric second metallic member, including a resilient hollow tube-like member adapted to be positioned within the first member, explosive means being positioned within the tube-like member, the explosive means being of such diameter that it fits closely to the wall of the bore of the tube-like member, and extends down a major portion of the length of the bore, a passageway extending transverse to and intersecting the :bore of the tube like member, explosive cord means positioned in the passageway which is in good physical contact with the explosive means, slit means within the tube-like member extending from the passageway to the periphery of the tube-like member throughout substantially a arc, by means of which the explosive cord means can be inserted into the passageway, the walls of the slit means being spaced sufiiciently close to each other that in order to insert the explosive cord means into the passageway it is necessary to temporarily bend the tube-like member, causing the walls of the slit means to spread apart.

2. The combination set forth in claim 1, wherein the resilient hollow tube-like member has a protrusion near one end, which protrusion can be used to accurately position the tube-like member within the first metallic tubular member.

3. The combination set forth in claim 1, wherein the resilient hollow tube-like member is closed at one end,

and there is an air gap of a predetermined length be- 7 tween the explosive means and the closed end.

References Cited UNITED STATES PATENTS 3,036,374 5/ 1962 Williams 29-421 3,131,467 5/1964 Thaller et a1. 29-421 3,140,537 7/1964 Popofi 29-4743 3,182,392 5/1965 Neal et al. 29-421 3,205,818 9/1965 Coulson 10227 3,290,771 12/1966 Silverman et al. 29-421 VERLIN R. PENDEGRASS, Primary Examiner.

US. Cl. X.R. 

